Question about process rlimits

[Artem Belevich]

Hi,

On Thu, Dec 2, 2010 at 12:51 PM, Andrew Duane <aduane at juniper.net> wrote:
>
> I've been poking at some bugs we have around pushing user memory to/past the limits of our box, and decided to try seeing what happens on a stock FreeBSD system (7.1 in this case).
>
> Basically I have a program that mallocs big memory chunks and zeros them to consume both physical and virtual memory. I had expected the program to stop malloc'ing when brk() reaches the process' RLIMIT_DATA (512MB cur and max). It didn't. It happily malloc'd many gigabytes of memory until I stopped it.
>
> On our 6.2 based product boxes, RLIMIT_DATA correctly stops the malloc from continuing, just like the manuals say.
>
> Am I missing something?

Perhaps that malloc has two ways of grabbing memory from system --
sbrk() and mmap() and they are subject to different limits. I believe
these days malloc is allowed to use both but prefers mmap which would
explain why RLIMIT_DATA didn't have much effect.

Try forcing malloc to use sbrk only via MALLOC_OPTIONS=Dm (not sure if
that's correct way to specify my intent, though).

--Artem